Surgery on the human eye has become commonplace in recent years. Many patients pursue eye surgery as an elective procedure, such as to avoid the use of contacts or glasses, and other patients may find it necessary to pursue surgery to correct an adverse condition in the eye. Such adverse conditions may include, for example, cataracts or presbyopia, as well as other conditions known to those skilled in the art that may negatively affect elements of the eye. For example, a cataract may increase the opacity of the natural lens of the eye, causing impaired vision or blindness. Correction of such adverse conditions may be achieved by surgically removing a cloudy or diseased lens in the patient's eye and replacing it with an artificial lens, known as an intraocular lens (IOL).
The anatomy and physiology of the human eye is well understood. Generally speaking, the structure of the human eye includes an outer layer formed of two parts, namely the cornea and the sclera. The middle layer of the eye includes the iris, the choroid, and the ciliary body. The inner layer of the eye includes the retina. The eye also includes, physically associated with the middle layer, a crystalline lens that is contained within an elastic capsule, referred to herein as the lens capsule, or capsular bag.
Image formation in the eye occurs by entry of image-forming light to the eye through the cornea, and refraction by the cornea and the crystalline lens to focus the image-forming light on the retina. The retina provides the light sensitive tissue of the eye.
Functionally, the cornea has a greater, and generally constant, optical power in comparison to the crystalline lens. The power of the crystalline lens, while smaller than that of the cornea, may be changed when the eye needs to focus at different distances. This change, or “accommodation,” is achieved by changing the shape of the crystalline lens. Accommodation, as used herein, includes the making of a change in the focus of the eye for different distances. For example, in order to change the shape of the crystalline lens for accommodation, the ciliary muscles may relax to cause ligaments (zonules) that support the crystalline lens to relax, thereby allowing the crystalline lens to become more rounded.
The iris operates to change the aperture size of the eye. More specifically, the diameter of the incoming light beam is controlled by the iris, which forms the aperture stop of the eye, and the ciliary muscles may contract, as referenced above, to provide accommodation in conjunction with any needed change in the size of the aperture provided by the iris. The opening, or aperture, in the iris is called the pupil.
Correction of defects or degradation in the aspects of the eye may occur surgically, as mentioned above, or non-surgically. In a simple example, it is common to wear glasses or contact lenses to improve vision by correcting myopic (near-sighted), hyperopic (far-sighted) and astigmatic eyesight. Rather than relying on glasses or contacts, elective laser refractive surgery, or other eye surgery, may serve to improve the refractive state of the eye, and may thereby decrease or eliminate dependence on glasses or contact lenses. Additional surgeries may include various methods of surgical remodeling of the cornea, or cataract surgery, for example. Surgery may also serve to implant an IOL, either in addition to the crystalline lens, which addition is referred to as a phakic IOL, or upon removal of the crystalline lens, which replacement is referred to as a pseudophakic IOL.
An IOL may be implanted in the eye, for example, as a replacement for the natural crystalline lens after cataract surgery, or to alter the optical properties of an eye in which the natural lens remains. IOLs often include an optic, and may preferably include at least one flexible fixation member, or haptic, that extends from the optic and becomes affixed in the eye to secure the lens in proper position to provide the desired vision correction. The optic typically includes an optically clear lens, and the opacity of the haptic may vary.
More specifically, the IOL may consist of a small plastic lens with haptics comprised of plastic side struts. The IOL may generally be made of an inflexible material, such as polymethyl methacrylate (PMMA), for example, or of a flexible material. The IOL may be a fixed monofocal lens matched to distance vision, or a multifocal lens that provides the recipient with multiple-focused vision at far and reading distances, for example. The IOL may also be a toric IOL to correct for astigmatism or an accommodating IOL that provides the recipient with vision at all distances (far, intermediate, and near) by moving and/or changing shape with the use of the muscles of the eye.
Flexible, softer materials may be preferred for the optic of the IOL, such as in order to allow for greater deformation, and thereby increased power change, in vivo. That is, the softer, more flexible materials mimic the mechanical properties of the natural lens material at a young age. However, with softer materials comes the concern that the optic may be more easily damaged, particularly during surgical insertion through a surgical incision and in placement and manipulation of the IOL in the capsular bag.
Implantation of an IOL into the eye involves making this surgical incision in the eye. Those skilled in the art will appreciate that it is advantageous to minimize the size of the surgical incision. Currently, the incision necessary for the insertion of a soft IOL may be in a range up to approximately 3.2-4.1 mm. A smaller incision reduces trauma to the eye and may speed healing and may reduce any surgically-related optical effects. However, as the size of the incision is decreased, there will arise a need to more compactly deliver lenses, particularly to avoid damage to the IOL during insertion through the smaller incision.
Further, insertion of a lens through the incision in the eye during a surgical procedure may cause post-operative inflammation, increased intraocular pressure, and/or posterior and anterior capsular opacification (PCO and ACO), and, for example, and these effects must be accounted for by the surgeon, both during and following surgery. If not accounted for, these effects may cause the onset of detrimental side effects, or may cause a failure to correct vision.
Thus, an implanted optic may be damaged upon insertion into the eye, and/or may cause temporary or permanent damage to the eye due to the insertion, thereby adversely affecting optical performance and/or cosmetic appearance. Likewise, surgical side effects that may cause such temporary damage from the insertion must be treated or prevented, preferably without further damage to the lens or the eye, or performance of the implanted optic may be adversely affected.
A need therefore exists to protect an implantable lens, such as an intraocular lens, comprised of a soft optic material, during insertion, and/or to negate the adverse side effects of implantation of a lens.